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Biomedical subjects

Q Liu

Publications and source records attributed to Q Liu.

At least 685 records · Page 38Linked to original sources
PubMed1993

Serotonin-like immunoreactivity in the adult and developing retina of the leopard frog Rana pipiens.

Recent work in nonmammalian vertebrate retinas has suggested that other cell types besides the generally accepted amacrine cells may contain serotonin. We have used immunocytochemical methods to study serotonin-like immunoreactivity (5-HTLI) in the retina of the developing and mature frog Rana pipiens. In the adult, two types of serotonin immunoreactive (5-HT-ir) cells were found in the inner nuclear layer (INL) of the retina. Additionally, a large population of cells in the retinal ganglion cell layer (RGCL) had 5-HTLI. These cells were grouped into three types based on their soma size and their primary dendritic branching pattern. The optic nerve fiber layer was also intensely stained with serotonin antisera although staining intensity decreased progressively as the fibers approached the optic nerve head. Severing the optic nerve resulted in 5-HT-ir elements that extended up the optic nerve shaft from the lesion site toward the retina. Both regional and temporal changes in the pattern of 5-HTLI were seen. In middle regions of retina, approximately 30% of the cells in the RGCL were 5-HT-ir. Nasal and temporal regions of central retina had significantly fewer 5-HT-ir cells. Early in development only scattered cells in the RGCL were 5-HT-ir. As the animals matured there was an increase in both the proportion and the staining intensity of these cells. Our results suggest that in studying the function and development of the visual system in this animal, the role of serotonin must be examined.

Animals↗
PubMed1993

Gene 5.5 protein of bacteriophage T7 inhibits the nucleoid protein H-NS of Escherichia coli.

Gene 5.5 of coliphage T7 is one of the most highly expressed genes during T7 infection. Gene 5.5 protein, purified from cells overexpressing the cloned gene, purifies with the nucleoid protein H-NS of Escherichia coli during three chromatographic steps. A fusion protein of gene 5.5 protein and maltose binding protein also purifies with H-NS. The fusion protein binds to the DNA-H-NS complex and abolishes H-NS-mediated inhibition of transcription by Escherichia coli and T7 RNA polymerases in vitro. Expression of gene 5.5 also relieves the repression of the Escherichia coli proU promoter by H-NS in vivo. The change of leucine to proline at residue 30 of gene 5.5 protein abolishes the interaction between gene 5.5 protein and H-NS.

ATP-Binding Cassette Transporters↗
PubMed1993

Indoor air pollution and lung cancer in Guangzhou, People's Republic of China.

A case-control study comprising 224 male and 92 female incident lung cancer cases and the same number of individually matched hospital controls was conducted from June 1983 to June 1984 in Guangzhou, People's Republic of China, to evaluate the association between indoor air pollution and lung cancer risk. Guangzhou residents were exposed to several sources of pollution in their homes, most importantly to cooking fumes. Increased risks were found among subjects living in a house without a separate kitchen (the exposure odds ratio was 2.4 (95% confidence interval (CI) 1.4-4.2) for men and 5.9 (95% CI 2.1-16.0) for women). Similarly, living in a house with poor air circulation was associated with an exposure odds ratio of 2.1 (95% CI 1.2-3.8) for men and 3.6 (95% CI 1.4-9.3) for women. A trend in the association between lung cancer risk and factors pertaining to house and kitchen ventilation was observed, and a decreasing risk of lung cancer was observed for several variables indicating better ventilation, even after adjustment for potential confounders such as education, occupation, living area, smoking, and history of chronic respiratory diseases. No statistically significant differences were found between cases and controls for frequency of cooking at home, presence of a chimney in the kitchen, or type of cooking fuel. Smoking was clearly related to risk of lung cancer in both men and women, and among nonsmoking women, exposure to tobacco smoke from their spouses was also associated with an increased risk. These results suggest that, in addition to smoking, indoor air pollution may be a risk factor for lung cancer.

Adult↗
PubMed1993

Developmental regulation and cell type-specific expression of the murine gamma F-crystallin gene is mediated through a lens-specific element containing the gamma F-1 binding site.

The mouse gamma F-crystallin gene, one of six differentially regulated members of the gamma-crystallin gene family, is expressed exclusively in central nuclear fiber cells of the adult lens. The expression of this gene is controlled through regulatory elements contained in two upstream enhancers and the proximal promoter. Here we show that while the upstream enhancers and the proximal promoter could each direct gene expression in fiber cells formed at early stages of lens growth and development, cooperation between these elements is required to achieve expression in fiber cells formed at later stages. Evidence is provided that cooperative interaction between these elements modulates gene expression by increasing promoter strength. We also show that sequences within the proximal promoter region that bind lens cell nuclear factor gamma F-1 are sufficient to elicit gene expression in central nuclear fiber cells of the adult lens.

Animals↗
PubMed1993

Factors contributing to reinfection with schistosomiasis japonica after treatment in the lake region of China.

The prevalence of schistosomiasis due to S. japonicum is focally high in the lake regions of China, and reinfection after treatment with praziquantel is frequent. In this study, the total reinfection rate among 740 treated persons was 12.9%. Factors associated with reinfection were age and sex, water contact and the distance from homes to snail habitats. The reinfection rate was higher among men (15.0%) than among women (8.3%). The frequency of water contact is the main factor in reinfection. Among persons with more than 120 and 10-120 water-contact days, the reinfection rates were 24.0% and 16.4%, respectively. The reinfection rates among people living 0 m, 500 m and 1000 m from snail-ridden areas were 14.1%, 8.3% and 4.3%, respectively. Fishing was the most frequent reason for water-contact, followed by herding animals and playing in water; reinfection rates among those engaging in these activities were 36.4%, 16.3% and 22.9%, respectively. Reinfection is clearly a problem, and since much of it is connected with essential economic activities, the cycle of infection and reinfection is not likely to be broken until effective methods for eliminating reservoirs of infection are developed.

Adolescent↗
PubMed1993

Genotypic and antigenic identification of two new strains of spotted fever group rickettsiae isolated from China.

Four isolates of spotted fever group rickettsiae isolated from ticks in China were compared with all known species and strains of spotted fever group rickettsiae by immunofluorescence assay, DNA polymerase chain reaction followed by restriction endonuclease fragment length polymorphism analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western immunoblot. The Chinese isolates belonged to three types, including a novel serotype which has not been described before. One isolate obtained from tick ova of Dermacentor nuttallii in Inner Mongolia was antigenically and genotypically identical to Rickettsia sibirica. Two isolates obtained from Dermacentor sinicus collected from Beijing were identical, different from other members of spotted fever group rickettsiae but apparently closely related to R. sibirica. HA-91, a strain isolated from Hyalomma asiaticum bv. kozlovi olenew, was antigenically and genotypically unique among spotted fever group rickettsiae, and we feel that data presented here should prompt consideration of it as a new species on the basis of current rickettsial taxonomy.

Animals↗
PubMed1993

The mouse retinoid-X receptor-gamma gene: genomic organization and evidence for functional isoforms.

Retinoid-X receptors (RXRs) are a subfamily of the steroid/thyroid nuclear receptor superfamily. There are three RXR genes: alpha, beta, and gamma, each with a distinct expression pattern and chromosomal location. In this study we describe the genomic organization of the mouse RXR gamma gene, identify a second mouse (m) RXR gamma isoform, and map the exons of the two mRXR gamma isoforms on the gene. The new mRXR gamma isoform, called gamma 2, has a unique 5'-untranslated region, and is expressed highly in both cardiac and skeletal muscles, but very little in the liver, while the mRXR gamma 1 is expressed in the brain and muscle. The gamma 2 isoform is also a functional receptor and can transactivate the retinoid response elements of the apolipoprotein-AI and cellular retinol-binding protein-II genes. The mRXR gamma gene spans at least 50 kilobases of DNA on mouse chromosome 1 and has nine introns ranging from 107 basepairs to more than 30 kilobases. From the genomic separation of the two unique 5'-ends of the mRXR gamma isoforms, it is suggested that this gene may have two promoters, similar to those described for the three RAR genes. The results of this study along with those of previously published studies suggest that there may be more than two isoforms of mRXR gamma.

Amino Acid Sequence↗
PubMed1993

Abnormal cytoskeletal and chromosome distribution in po, ms4 and ms6; mutant alleles of polymitotic that disrupt the cell cycle progression from meiosis to mitosis in maize.

The maize cell cycle regulation mutant polymitotic (po) progresses through abnormal cell cycles, characterized by premature cell divisions without chromosome duplication of the daughter cells produced by meiosis during microsporogenesis and macrosporogenesis. There are three recessive alleles of the Po gene; po, ms4, and ms6. A new method of permeabilizing cells based on freeze-fracture technology was used to study the distribution of microtubules in wild-type and mutant microspores. Here we show that an abnormal distribution of microtubules is correlated with changes in chromosome morphology in a cell cycle-dependent manner in po, ms4 and ms6 mutant alleles. After meiosis II, the cell cycle is complete and becomes progressively less synchronous in po homozygotes compared with wild-type cells. During microsporogenesis, the distribution of microtubules is abnormal, and chromosome morphology is altered in both po, ms4 and ms6 mutants. However, more chromosome fragments or micronuclei associated with minispindles are present in ms6 than po and ms4. After microspores are released from the tetrads, disruptions in structure and organization of chromosomes and microtubules continues in subsequent abnormal cell cycles. However, these cell cycles are incomplete since phragmoplasts are not formed. During these incomplete cell cycles, abnormal spindles and microtubule arrays are induced and extra microtubule arrays are associated with irregularly distributed chromosome fragments. States corresponding to interphase, prophase, metaphase and anaphase can be recognized in the mutant microspores. Abnormal cell cycles also occur after female meiosis during ms4 macrospore development. Since only the cell that normally undergoes embryo sac development (the chazal-most cell) undergoes supernumerary divisions this suggests that the po phenotype can be characterized as premature haploid divisions rather than repetition of meiosis II.

Cell Compartmentation↗
PubMed1993

A gray system decision model of the multiple factors for the educational levels among regional population.

"Using 1% statistics and 10% sample aggregate data of the fourth census, the authors analyze various comprehensive indexes reflecting the educational levels among the Chinese population, on the basis of which a multi-regional gray system decision model is established. The authors also conduct a preliminary analysis of the results of the calculation." Grayness is defined here as "incompleteness and uncertainty of information."

Asia↗
PubMed1993

Study on application of the silicone oil in the reattachment of complicated retinal detachment.

Sixty eyes with complicated retinal detachment were treated by vitrectomy combined with silicone oil tamponade (27 eyes of PVR grade D, 15 eyes of giant retinal tears with posterior flat folded-over, 13 eyes of posterior or macular hole, 5 eyes of traumatic PVR). After 3-24 months follow-up, the study showed retinal anatomic reattachment in 48 eyes in which the visual acuity of 32 eyes was 0.05 or better. The authors consider that vitrectomy and peeling make the silicone oil tamponade perfect the vitreous surgery and improve the successful rate. The theory of silicone oil tamponade, the indications, advantages and disadvantages of silicone oil tamponade are discussed in this paper.

Adolescent↗
PubMed1993

Long-term results of surgical treatment for acute hemorrhagic necrotizing pancreatitis.

Eighteen patients with acute hemorrhagic necrotizing pancreatitis who survived from operation were followed up for 12 to 43 months. Late complications including pancreatic external fistula, pseudocyst, hyperglycemia, etc were reviewed. The pancreatic juice was collected through endoscopic cannulation. The volume and HCO3- concentration of the pancreatic juice and three kinds of pancreatic enzymes were measured. The results demonstrated that inspite of anatomic abnormality or functional impairment of the pancreas, the pancreatic insufficiency rarely manifested to be marked because of the compensative ability of the viable exocrine pancreas.

Acute Disease↗
PubMed1993

[Application of in situ hybridization using digoxigenin--labeled HBV DNA probe and comparison with biotinylated probe].

A method of in situ hybridization for HBV DNA on liver tissue with digoxigenin-labeled probe is described. We have detected the HBV DNA of sixteen liver biopsies. The results showed that the sensitivity and specificity of digoxigenin-labeled probe for in situ hybridization were hig er and stronger then those of biotinylated probe. The practicality of digoxigenin-labeled probe is better. It is an excellent non-radioactive probe for in situ hybridization, which may eventually replace the biotinylated probe. The localization of HBV DNA in hepatocytes could be classified into 4 types, namely, the whole cytoplasmic, focal cytoplasmic, whole nucleic and nuclear membranous-nucleolus. The results of in situ hybridization using digoxigenin-labeled probe could reflect the free or integrated status of HBV genome and the levels of its genomic replication in hepatocytes. The procedure of in situ hybridization using digoxigeninlabeled probe was also discussed.

Biotin↗
PubMed1993

Progressive and regressive fate of lens tumors correlates with subtle differences in transgene expression in gamma F-crystallin-SV40 T antigen transgenic mice.

Regulatory elements of the mouse gamma F-crystallin gene were used to derive transgenic mice expressing SV40 large T antigen in terminally differentiating fiber cells of the ocular lens. The resulting gamma F-crystallin-T antigen mice developed either malignant or regressive lens tumors in a strain-dependent fashion. Developmental and RNA analyses revealed that in both 'tumor-progressing' and 'tumor-regressing' mouse strains expression of the transgene blocked morphological differentiation of lens fibers without appreciably affecting gamma-crystallin gene expression, a marker of terminal lens fiber cell differentiation. Strain-dependent differences in tumorigenic outcome could be correlated with both subtle differences in transgene expression and the ability of tumor cells to escape from the normal confines of the lens. The results implicate the importance of cellular environment to malignant tumor development and provide insight into those features of normal lens ontogeny that may render the lens refractory to the development of spontaneous tumors.

Animals↗
PubMed1993

"Cryptic" repeating triplets of purines and pyrimidines (cRRY(i)) are frequent and polymorphic: analysis of coding cRRY(i) in the proopiomelanocortin (POMC) and TATA-binding protein (TBP) genes.

Triplets of the form of purine, purine, pyrimidine (RRY(i)) are enhanced in frequency in the genomes of primates, rodents, and bacteria. Some RRY(i) are "cryptic" repeats (cRRY(i)) in which no one tandem run of a trinucleotide predominates. A search of human GenBank sequence revealed that the sequences of cRRY(i) are highly nonrandom. Three randomly chosen human cRRY(i) were sequenced in search of polymorphic alleles. Multiple polymorphic alleles were found in cRRY(i) in the coding regions of the genes for proopiomelanocortin (POMC) and TATA-binding protein (TBP). The highly polymorphic TBP cRRY(i) was characterized in detail. Direct sequencing of 157 unrelated human alleles demonstrated the presence of 20 different alleles which resulted in 29-40 consecutive glutamines in the amino-terminal region of TBP. These alleles are differentially distributed among the races. PCR was used to screen 1,846 additional alleles in order to characterize more fully the range of variation in the population. Three additional alleles were discovered, but there was no example of a substantial sequence amplification as is seen in the repeat sequences associated with X-linked spinal and bulbar muscular atrophy, myotonic dystrophy, or the fragile-X syndrome. The structure of the TBP cRRY(i) is conserved in the five monkey species examined. In the chimpanzee, examination of four individuals revealed that the cRRY(i) was highly polymorphic, but the pattern of polymorphism differed from that in humans. The TBP cRRY(i) displays both similarities with and differences from the previously described RRY(i) in the coding sequence of the androgen receptor. Our data suggest how simple tandem repeats could evolve from cryptic repeats.

Aged↗
PubMed1992

Transforming growth factor beta (TGF-beta) type V receptor has a TGF-beta-stimulated serine/threonine-specific autophosphorylation activity.

The transforming growth factor beta (TGF-beta) type V receptor, a newly identified high molecular weight TGF-beta receptor (M(r) approximately 400,000) has been purified from bovine liver plasma membranes (O'Grady, P., Kuo, M.-D., Baldassare, J. J., Huang, S. S., and Huang, J. S. (1991) J. Biol. Chem. 266, 8583-8589). The purified TGF-beta type V receptor underwent autophosphorylation at serine residues when incubated with [gamma-32P]ATP in the presence of 0.1% beta-mercaptoethanol and 2.5 mM MnCl2. This phosphorylation was stimulated by preincubation with TGF-beta. The preferred exogenous substrate for the Ser/Thr-specific phosphorylation activity of the type V receptor was found to be bovine casein. The TGF-beta type V receptor could be affinity-labeled with 5'-p-[adenine-8-14C]fluorosulfonylbenzoyl adenosine. Polylysine appeared to stimulate the autophosphorylation of the TGF-beta type receptor in the presence of [gamma-32P]ATP and the incorporation of 5'-p-[adenine-8-14C]fluorosulfonylbenzoyl adenosine into the TGF-beta type V receptor. The amino acid sequence analysis of the peptide fragments produced by cyanogen bromide cleavage of the purified TGF-beta type V receptor revealed that a peptide, namely CNBr-19, contained an amino acid sequence which shows homology to the putative ATP binding site of the receptors for activin, the Caenorhabditis elegans daf-1 gene product, and TGF-beta type II receptor (Lin, H. Y., Wang, Y.-F., Ng-Eaton, E., Weinberg, R. A., and Lodish, H. F. (1992) Cell 68, 775-785). These results suggest that the TGF-beta type V receptor is a Ser/Thr-specific protein kinase and belongs to the new class of membrane receptors associated with a Ser/Thr-specific protein kinase activity.

Adenosine↗
PubMed1992

Prolactin synthesized and secreted by human peripheral blood mononuclear cells: an autocrine growth factor for lymphoproliferation.

Prolactin has been shown to have an immunoregulatory role in the rodent immune response. A prolactin-like molecule has also been found in mouse splenocytes and a human B-lymphoblastoid cell line. We have evaluated whether human peripheral blood mononuclear cells (PBMCs) synthesize and/or secrete prolactin. We used the polymerase chain reaction (PCR) to generate a 276-base-pair prolactin product from human PBMCs, and Southern blot analysis confirmed that it was related to prolactin. Western blotting using a polyclonal antibody to prolactin indicated that cell extracts prepared from human PBMCs contained a high molecular mass (60-kDa) immunoreactive prolactin. To determine whether this PBMC prolactin was being secreted, we developed a highly sensitive and specific hormonal enzyme-linked immunoplaque assay. With this assay, we were able to detect human prolactin secretion from concanavalin A (Con A)- or phytohemagglutinin-stimulated PBMCs but not from unstimulated PBMCs. We next sought to determine whether this secreted prolactin could function as an autocrine growth factor in lymphoproliferation. We observed that anti-human prolactin antiserum significantly inhibited human PBMC proliferation in response to Con A or phytohemagglutinin. We conclude that a prolactin-like molecule is synthesized and secreted by human PBMCs and that it functions in an autocrine manner as a growth factor for lymphoproliferation.

Base Sequence↗
PubMed1992

Identification of the 12-O-tetradecanoylphorbol-13-acetate-responsive enhancer of the MS gene of the Epstein-Barr virus.

We previously located two 12-O-tetradecanoylphorbol-13-acetate (TPA)-responsive enhancers, MSTRE-I and MSTRE-II, in the upstream sequence of the MS gene of Epstein-Barr virus (Liu, Q., and Summers, W.C. (1989) J. Virol. 63, 5062-5068). The core sequence of the MSTRE-I enhancer is now determined to be between -718 and -708 of the upstream sequence of the MS gene. The activity of the enhancer is also sensitive to its immediate surrounding sequence on either side. A single copy of a 30-base pair (bp) fragment containing the MSTRE-I sequence was able to confer TPA responsiveness upon the MS promoter even in the absence of an AP-1 binding site. Multiple tandem copies of this 30-bp fragment, regardless of their relative orientations to each other, could function synergistically to enhance the MS promoter activity. At least two copies of the 30-bp fragment were required to bestow TPA induction upon the thymidine kinase gene promoter of herpes simplex virus type 1. The MSTRE-I sequence could also be bound by a Fos-GCN4 chimeric protein but with an affinity much lower than that between the chimeric protein and the AP-1 binding site. This MSTRE-I region has strong homology to one of the TPA-responsive elements (the ZII domain) in the upstream sequence of the EBV BZLF1 gene. In addition, a putative negative regulatory region or silencer was found immediately downstream of the MSTRE-I enhancer. This potential silencer region contains a 14-bp sequence that is homologous to the silencer consensus sequence of the BZLF1 gene. Therefore, the regulation of the MS gene may share the same pathway with the immediate early gene BZLF1.

Autoradiography↗